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Department Environmental Chemistry

On the trail of pollutants

Our research team studies the presence, distribution and fate of organic pollutants in the aquatic environment. The focus of our research is on substance flux from urban areas and from agriculture, and the main tools that we use for this work are trace analysis, field and laboratory studies and modelling.

Latest publications

Plants or bacteria? 130 years of mixed imprints in Lake Baldegg sediments (Switzerland), as revealed by compound-specific isotope analysis (CSIA) and biomarker analysis

Soil erosion and associated sediment transfer are among the major causes of aquatic ecosystem and surface water quality impairment. Through land use and agricultural practices, human activities modify the soil erosive risk and the catchment connectivity, becoming a key factor of sediment dynamics. Hence, restoration and management plans of water bodies can only be efficient if the sediment sources and the proportion attributable to different land uses are identified. According to this aim, we applied two approaches, namely compound-specific isotope analysis (CSIA) of long-chain fatty acids (FAs) and triterpenoid biomarker analysis, to a eutrophic lake, Lake Baldegg, and its agriculturally used catchment (Switzerland). Soils reflecting the five main land uses of the catchment (arable lands, temporary and permanent grasslands, mixed forests, orchards) were subjected to CSIA. The compound-specific stable isotope δ13C signatures clearly discriminate between potential grasslands (permanent and temporary) and forest sources. Signatures of agricultural land and orchards fall in between. The soil signal was compared to the isotopic signature of a lake sediment sequence covering ca. 130 years (before 1885 to 2009). The recent lake samples (1940 to 2009, with the exception of 1964 to 1972) fall into the soil isotopic signature polygon and indicate an important contribution of the forests, which might be explained by (1) the location of the forests on steep slopes, resulting in a higher connectivity of the forests to the lake, and/or (2) potential direct inputs of trees and shrubs growing along the rivers feeding the lake and around the lake. However, the lake sediment samples older than 1940 lie outside the source soils' polygon, as a result of FA contribution from a not yet identified source, most likely produced by an in situ aquatic source, either algae, bacteria or other microorganisms or an ex-site historic source from wetland soils and plants (e.g. Sphagnum species). Despite the overprint of the yet unknown source on the historic isotopic signal of the lake sediments, land use and catchment history are clearly reflected in the CSIA results, with isotopic shifts being synchronous with changes in the catchment, land use and eutrophication history. The investigated highly specific biomarkers were not detected in the lake sediment, even though they were present in the soils. However, two trimethyltetrahydrochrysenes (TTHCs), natural diagenetic products of pentacyclic triterpenoids, were found in the lake sediments. Their origin is attributed to the in situ microbial degradation of some of the triterpenoids. While the need to apportion sediment sources is especially crucial in eutrophic systems, our study stresses the importance of exercising caution with CSIA and triterpenoid biomarkers in such environments, where the active metabolism of bacteria might mask the original terrestrial isotopic signals.

Climate change and freshwater ecosystems. Impacts on water quality and ecological status

Climate change is one of the largest and possibly most impactful ongoing but also future environmental drivers. Understanding effects of climate change on aquatic ecosystems and their function is thus of high importance. Within the framework of the Hydro-CH2018 project, the Swiss Federal Office for the Environment (FOEN) initiated a synthesis of climate change effects on water quality and the ecological status of freshwater ecosystems. The present report is the result of these synthesis efforts.

Our goal was to summarize available knowledge on how climatic change affects freshwater ecosystems in Switzerland. The work was performed between fall 2017 and fall 2018. We aimed to provide a synthesis of existing knowledge that is as consistent and complete as possible, but also to identify possible knowledge gaps. The work is based on extensive literature surveys and expert interviews. Whenever possible, we included quantitative conclusions. At the same time, we also wanted to be specific and relevant for natural Swiss water systems, so we also included qualitative effects and case studies. While many of the major ongoing and expected effects of climate change on aquatic systems are already well known, we also faced several challenges. For example: (i) some effects of climate change are still only partly understood, (ii) many of the focal endpoints, both with respect to water quality and ecological status, are not only affected by climate change, but also by other anthropogenic drivers, and disentangling these drivers is challenging if not infeasible, (iii) specific effects can be dependent on specific local factors, and (iv) the research field is so vast that the available resources for this one-year synthesis did not allow us to go into as much detail and data analysis as the topic would deserve. As a result, our report is a snapshot of scientific knowledge, at the period of realization, of the effects of climate change on aquatic ecosystems in Switzerland, set into the context of other environmental drivers.

While we see that climate change will have major effects on Swiss water systems, we also identify possible ways of mitigating these effects. We thereby hope that our synthesis is not only an overview of current and future changes, but will also help in policy- and decisionmaking about how to best deal with these changes and challenges.

Manganese exposure and working memory-related brain activity in smallholder farmworkers in Costa Rica: results from a pilot study

Main sources of manganese (Mn) in the general population are diet and drinking water. Mn is also found in ethylene bisdithiocarbamate (EBDC) fungicides used in agriculture or emitted into the air by ferromanganese plants and welding fumes, which can be additional environmental and occupational sources of exposure. High occupational Mn exposure has been linked with motor, behavioral, and cognitive impairment, but its effects on neural function remain poorly understood. We conducted a functional neuroimaging study in a sample of 48 farmworkers in Zarcero County, Costa Rica, an agricultural region where EBDC fungicides are sprayed. We measured Mn concentrations in farmworkers’ toenails (n = 40 farmworkers) and hair (n = 33 farmworkers), and recorded brain activity in the dorsolateral prefrontal cortex during a letter-retrieval working memory task using functional near-infrared spectroscopy (fNIRS). We estimated exposure-outcome associations using multivariable linear regression models adjusted for age and education level. Geometric mean (geometric standard deviation) toenail and hair Mn concentrations were 0.40 μg/g (3.52) and 0.24 μg/g (3.54), respectively. We did not find strong evidence that Mn concentrations were associated with working memory-related brain activity in this sample of farmworkers; we also found null associations between working memory task accuracy and brain activity. However, our small sample size may have limited our ability to detect small effect sizes with statistical precision. Our study demonstrates that fNIRS can be a useful and feasible tool in environmental epidemiology for examining the effects of toxicants, like Mn, on neural function. This may prove to be important for elucidating neuropathological pathways that underlie previously reported associations of elevated Mn exposure with neurotoxic effects.

Vacuum-assisted evaporative concentration combined with LC-HRMS/MS for ultra-trace-level screening of organic micropollutants in environmental water samples

Vacuum-assisted evaporative concentration (VEC) was successfully applied and validated for the enrichment of 590 organic substances from river water and wastewater. Different volumes of water samples (6 mL wastewater influent, 15 mL wastewater effluent, and 60 mL river water) were evaporated to 0.3 mL and finally adjusted to 0.4 mL. 0.1 mL of the concentrate were injected into a polar reversed-phase C18 liquid chromatography column coupled with electrospray ionization to high-resolution tandem mass spectrometry. Analyte recoveries were determined for VEC and compared against a mixed-bed multilayer solid-phase extraction (SPE). Both approaches performed equally well (≥ 70% recovery) for a vast number of analytes (n = 327), whereas certain substances were especially amenable to enrichment by either SPE (e.g., 4-chlorobenzophenone, logDow,pH7 4) or VEC (e.g., TRIS, logDow,pH7 − 4.6). Overall, VEC was more suitable for the enrichment of polar analytes, albeit considerable signal suppression (up to 74% in river water) was observed for the VEC-enriched sample matrix. Nevertheless, VEC allowed for accurate and precise quantification down to the sub-nanogram per liter level and required no more than 60 mL of the sample, as demonstrated by its application to several environmental water matrices. By contrast, SPE is typically constrained by high sample volumes ranging from 100 mL (wastewater influent) to 1000 mL (river water). The developed VEC workflow not only requires low labor cost and minimum supervision but is also a rapid, convenient, and environmentally safe alternative to SPE and highly suitable for target and non-target analysis.

News

Excessive levels of plant protection products in small streams

April 2, 2019Two studies by Eawag and the Ecotox Centre have once again shown that surface waters in agricultural catchment areas are heavily contaminated with plant protection products. Concentrations of individual substances persisting for several months pose a risk of chronic toxicity and, for extended periods, exceed the levels at which a risk of acute toxicity exists for aquatic plants and organisms. In most of the samples, 30 or more different active ingredients were detected. Studies of stream biodiversity and bioassays confirmed the threat posed by these mixtures of substances... [read more]